Zoom lens

ABSTRACT

A compact zoom lens, which can attain a compact lens system while maintaining a simple lens arrangement including six lenses, and can minimize deterioration of performance caused by a variation upon assembling, is disclosed. The compact zoom lens includes a positive first lens group G 1  and a negative second lens group G 2 . The first lens group G 1  has, in turn from the object side, a positive meniscus lens component L 1  with the convex surface facing the object side, a meniscus-shape junction negative lens component L 2  constituted by a double-concave negative lens component L 2n  and a double-convex positive lens component L 2p , and a double-convex positive lens component L 3 . The second lens group G 2  has, in turn from the object side, a positive meniscus lens component L 4  with the convex surface facing the image side, and a negative meniscus lens component L 5  with the convex surface facing the image side, and at least one lens surface of the second lens group G 2  is formed to have an aspherical surface shape. The zoom lens satisfies six conditions.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a zoom lens suitable for a compact camera.

2. Related Background Art

As a photographing lens for a recent lens shutter type compact camera, a zoom lens tends to be popular. In a zoom lens of this type, a compact and low-cost structure is demanded in correspondence with a compact and low-cost structure of the camera main body. For example, U.S. Pat. No. 4,929,069 discloses a zoom lens, which is constituted by as a small number of lenses as six lenses, and can attain low cost and a certain compact structure.

However, the zoom lens disclosed in U.S. Pat. No. 4,929,069 is larger than a two-focal point switching lens as a popular lens in a conventional multi-functional compact camera, and the size of a camera itself equipped with this lens is also increased. Since a conventional zoom lens suffers from relatively serious deterioration of performance due to a variation in assembling, a long assembling/adjustment time is required to realize performance as designed, resulting in relatively low productivity.

SUMMARY OF THE INVENTION

It is, therefore, an object of the present invention to provide a zoom lens, which has a further compact lens system while maintaining a simple lens structure constituted by about six lenses, and has high productivity with relatively small influence on performance due to a variation in assembling.

In order to achieve the above object, according to one aspect of the present invention, there is provided a zoom lens, which includes a first lens group G₁ having a positive refracting power and a second lens group G₂ having a negative refracting power, and performs a zooming operation from a wide-angle end to a telephoto end by decreasing a space between the first and second lens groups G₁ and G₂, wherein

the first lens group G₁ has, in order from an object side,

a positive meniscus lens component L₁ with a convex surface facing the object side,

a cemented negative lens component L₂ constituted by a double-concave negative lens component L_(2n) and a double-convex positive lens component L_(2p), and having a meniscus shape as a whole, and

a double-convex positive lens component L₃,

the second lens group G₂ has, in order from the object side,

a positive meniscus lens component L₄ with a convex surface facing an image side, and

a negative meniscus lens component L₅ with a convex surface facing the image side, and

the zoom lens is arranged to satisfy the following conditions:

    0.09<dL.sub.2 /f.sub.W <0.18                               (1)

    0.45<(nL.sub.2n -nL.sub.2p)·f.sub.W /r.sub.4 <0.9 (2)

    -4<fL.sub.2 /f.sub.1 <-1.8                                 (3)

    1.1<fL.sub.3 /f.sub.1 <1.6                                 (4)

where

f_(W) : the focal length of the entire system at the wide-angle end

dL₂ : the axial lens thickness of the cemented negative lens component L₂ in the first lens group G₁

nL_(2n) : the refractive index of the double-concave negative lens component L_(2n) forming the cemented negative lens component L₂ in the first lens group G₁

nL_(2p) : the refractive index of the double-convex positive lens component L_(2p) forming the cemented negative lens component L₂ in the first lens group G₁

r₄ : the radius of curvature of the cemented surface in the cemented negative lens component L₂ in the first lens group G₁

fL₂ : the focal length of the cemented negative lens component L₂ in the first lens group G₁

fL₃ : the focal length of the double-convex positive lens component L₃ in the first lens group G₁

f₁ : the focal length of the first lens group G₁.

In the zoom lens constituted by the two, i.e., positive and negative lens groups with the above arrangement, a positive distortion at the wide-angle side normally tends to be increased. In particular, like in the present invention, when the second lens group G₂ is constituted by as a small number of lenses as two lenses, the positive distortion is easily generated in the second lens group G₂.

Therefore, in order to correct the distortion in the entire lens system, a negative distortion must be generated in the first lens group G₁.

For this purpose, it is preferable that the cemented negative lens component L₂ effective generates a negative distortion while suppressing generation of a positive distortion in the positive lens component L₁ located at the most object side. Thus, the positive lens component L₁ is formed to have a meniscus shape with the convex surface facing the object side, so that the incident and exit angles of a principal ray outside the optical axis (the central ray of an oblique light beam) passing the object- and image-side surfaces of the positive lens component L₁ with respect to the normals to the two lens surfaces are not increased, thereby preventing the principal ray outside the optical axis from being refracted largely.

On the other hand, the cemented negative lens component L₂ has the concave object-side surface to largely refract the principal ray outside the optical axis.

In order to suppress generation of the positive distortion in the second lens group G₂ having the negative refracting power, the negative lens component L₅ is formed to have a meniscus shape with the concave surface facing the object side, so that the incident angle of the principal ray outside the optical axis with respect to the normal to the lens surface is decreased.

With the above arrangement, the present invention is advantageous for the distortion.

In the present invention, the negative lens component L₂ in the first lens group G₁ comprises a cemented lens constituted by the double-concave negative lens L_(2n) and the double-convex positive lens L_(2p), thereby effectively correcting a spherical aberration and a chromatic aberration. In particular, PG,7 since the negative lens component L₂ has a cemented surface having a positive radius of curvature, a fluctuation of a chromatic aberration of magnification generated upon zooming can be suppressed. Furthermore, as compared to a case wherein the negative lens L_(2n) and the positive lens L_(2p) are separated, a cause for deteriorating performance due to decentering can be removed, thus improving productivity.

In the present invention, since the second lens group G₂ has the negative refracting power, a positive spherical aberration is easily generated in the second lens group G₂. In particular, when a zooming operation is performed from the wide-angle end toward the telephoto end, the spherical aberration tends to increase in the positive direction.

Therefore, in order to suppress a fluctuation of a spherical aberration upon zooming, a negative spherical aberration must be intentionally generated in the positive lens component L₄ located at the object side in the second lens group G₂ so as to satisfactorily correct the spherical aberration in the second lens group G₂. For this purpose, the positive lens component L₄ is formed to have a meniscus shape with the convex surface facing the image side so as to generate many negative spherical aberration components, thereby correcting the fluctuation of the spherical aberration upon zooming with a good balance. In addition, the positive lens component L₄ is advantageous for correction of an astigmatism and a coma since it has a shape for decreasing the incident angle of the principal ray outside the optical axis with respect to the normal to the lens surface.

Under the assumption of the detailed lens shapes in the lens groups described above, the conditions (1) to (4) according to the present invention are set for the following reasons.

The condition (1) defines the axial lens thickness of the cemented negative lens component L₂ in the first lens group G₁, which thickness is suitable for achieving both a compact lens system and correction of a positive distortion at the wide-angle end.

When the axial lens thickness of the lens component L₂ exceeds the upper limit of the condition (1), the size of the first lens group G₁ is increased, and the size of the camera as a whole is undesirably increased.

When the axial lens thickness of the lens component L₂ is set below the lower limit of the condition (1), the distance between the object-side surface of the cemented negative lens component L₂ and an aperture stop arranged immediately after the first lens group G₁ is decreased, it becomes difficult to effectively generate a negative distortion at the object-side surface of the junction negative lens component L₂, and the positive distortion generated in the second lens group cannot be canceled.

The condition (2) defines a range of the refracting power at the cemented surface of the cemented negative lens component L₂ in the first lens group G₁, which range is suitable for satisfactorily correcting a spherical aberration, a coma, and the like.

When the refracting power is set below the lower limit of the condition (2), the refracting power at the cemented surface of the cemented negative lens component L₂ is decreased, and the spherical aberration cannot be satisfactorily corrected. As a result, it becomes difficult to perform well-balanced aberration correction including various other aberrations.

On the other hand, when the refracting power is set above the upper limit of the condition (2), the refracting power at the cemented surface of the cemented negative lens component L₂ is increase too much. As a result, a coma is generated at the wide-angle end, and a so-called negative coma state undesirably occurs.

The conditions (3) and (4) define the power distribution of the lens components in the first lens group G₁ so as to attain a compact zoom lens structure, improved productivity, and satisfactory correction of various aberrations at the same time.

Of these conditions, the condition (3) defines the focal length fL₂ of the cemented negative lens component L₂ in the first lens group G₁. When the cemented negative lens component L₂ is formed to have a relatively large focal length, even when the cemented negative lens component L₂ is relatively decentered or inclined in the first lens group G₁, image formation performance is not easily deteriorated, and this leads to improvement of productivity.

When the focal length exceeds the upper limit of the condition (3), the focal length of the cemented negative lens component L₂ is decreased, and the above-mentioned effect cannot be obtained.

When the focal length is set below the lower limit of the condition (3), the negative refracting power of the cemented negative lens component L₂ is weakened, and it becomes difficult to satisfactorily correct various aberrations such as a spherical aberration.

The condition (4) defines the focal length fL₃ of the double-convex positive lens component L₃ in the first lens group G₁. Since the negative refracting power of the cemented negative lens component L₂ in the first lens group G₁ is relatively weakened by the condition (3), the refracting power of the double-convex positive lens component L₃ can also be weakened as compared to the refracting power of the first lens group G₁.

For this reason, as in the case of the cemented negative lens component L₂, even when the positive lens component L₃ is relatively decentered or inclined, image formation performance is not easily deteriorated, and this leads to improvement of productivity.

When the focal length exceeds the upper limit of the condition (4), the refracting power of the positive lens component L₃ becomes too weak, and the rear-side principal point of the first lens group G₁ is separated farther toward the object side from the final lens surface of the first lens group G₁. For this reason, when a zooming operation is performed toward the telephoto side, the first and second lens groups G₁ and G₂ tend to mechanically interfere with each other, and consequently, a sufficient zoom ratio cannot be obtained.

When the focal length is set below the lower limit of the condition (4), the refracting power of the positive lens component L₃ becomes too strong, and performance is considerably deteriorated when the positive lens component L₃ is decentered or inclined, resulting in poor productivity. Since the rear-side principal point of the first lens group G₁ is located near the final lens surface of the first lens group G₁ or is located at the image side of the final lens surface, the total lens length is prolonged, thus disturbing the compact structure.

The zoom lens according to the present invention preferably satisfies the following conditions in addition to the above-mentioned conditions (1) to (4).

    0.5<Σd.sub.W /f.sub.W <0.85                          (5)

    2<fL.sub.1 ·L.sub.2 /f.sub.1 <9                   (6)

where

Σd_(W) : the axial lens thickness from the most object-side lens surface to the most image-side lens surface in the zoom lens at the wide-angle end

fL₁ ·L₂ : the composite focal length of the positive meniscus lens component L₁ and the cemented negative lens component L₂ in the first lens group G₁.

The condition (5) defines the axial lens thickness from the first lens surface to the final lens surface in the lens system at the wide-angle end, which thickness is suitable for attaining a compact lens system. When the axial lens thickness exceeds the upper limit of the condition (5), the total lens length at the wide-angle end is undesirably increased. When the axial lens thickness is to be decreased below the lower limit of the condition (5), the following three techniques may be proposed.

1 The axial lens thickness of the first lens group G₁ is decreased. In consideration of a condition such as a lens edge thickness, the thickness of the cemented negative lens component L₂ is decreased in practice.

2 The space between the first and second lens groups G₁ and G₂ is decreased.

3 The axial lens thickness of the second lens group G₂ is decreased. In practice, the space between the positive meniscus lens component L₄ and the negative meniscus lens component L₅ in the second lens group G₂ is decreased.

Of these techniques, with the technique 1, the distance between the object-side surface of the cemented negative lens component L₂ and the aperture stop arranged immediately after the first lens group G₁ becomes small, and it becomes difficult to effectively generate the negative distortion at the object-side surface of the cemented negative lens component L₂. As a result, the positive distortion generated in the second lens group G₂ cannot be canceled. With the technique 2, since the variable range of the group interval between the first and second lens groups G₁ and G₂ becomes small, a sufficient zoom ratio cannot be obtained.

Furthermore, with the technique 3, the difference between the height from the optical axis where a ray from the axial object point passes through the positive meniscus lens component L₄ in the second group G₂ and the height from the optical axis where the ray passes through the negative meniscus lens component L₅ becomes small, and it becomes difficult to satisfactorily correct a spherical aberration. Therefore, when the axial lens thickness is set below the lower limit of the condition (5), satisfactory correction can be made by none of the techniques 1, 2, and 3.

The condition (6) is a condition for reliably obtaining the effect of the conditions (3) and (4), and defines the composite focal length fL₁ ·L₂ of the positive meniscus lens component L₁ and the cemented negative lens component L₂ in the first lens group G₁.

When the focal length exceeds the upper limit of limit of the condition (6), the composite focal length fL₁ ·L₂ is prolonged, and the refracting power of the double-convex lens component L₃ must be strengthened accordingly. In this case, productivity is impaired, and the total lens length is undesirably increased like in the case wherein the focal length is set below the lower limit of the condition (4).

When the focal length is decreased below the lower limit of the condition (6), the composite focal length fL₁ ·L₂ is shortened, and the refracting power of the double-convex positive lens component L₃ must be weakened. In this case, a sufficient zoom ratio cannot be obtained like in the case wherein the focal length exceeds the upper limit of the condition (4).

When the composite power of the positive meniscus lens component L₁ and the cemented negative lens component L₂ is set to be a positive power according to the condition (6), the height where a ray from the axial object point passes through the double-convex positive lens component L₃ is lowered, and the lens diameter of the double-convex positive lens component L₃ can be decreased. Similarly, the full-open diameter of the aperture stop arranged immediately after the double-convex positive lens component L₃ can also be decreased, and the diameter of the entire zoom lens can be effectively decreased.

Furthermore, in the zoom lens according to the present invention, at least one lens surface in the second lens group G₂ is preferably formed as an aspherical surface. In addition, the spherical surface shape is preferably a one with which the positive refracting power is gradually increased from the center toward the peripheral portion of the lens, or a one with which the negative refracting power is gradually decreased from the center toward the peripheral portion of the lens.

When the aspherical surface in the second lens group G₂ is formed as described above, generation of the positive distortion in the second lens group G₂ can be suppressed. Furthermore, this aspherical surface shape is advantageous for correction of a spherical aberration since it is convenient for correcting the positive spherical aberration generated in the second lens group G₂.

When an axial chromatic aberration and a chromatic aberration of magnification are to be corrected with a good balance under the above-mentioned condition (2), the Abbe's numbers of the negative and positive lens components L_(2n) and L_(2p) forming the junction negative lens component L₂ are preferably set to satisfy the following condition (7):

    17<νL.sub.2p -νL.sub.2n <30                          (7)

where νL_(2p) and νL_(2n) are defined as follows:

νL_(2p) : the Abbe's number of the double-convex positive lens component L_(2p) forming the cemented negative lens component L₂ in the first lens group G₁

νL_(2n) : the Abbe's number of the double-concave negative lens component L_(2n) forming the cemented negative lens component L₂ in the first lens group G₁.

Other objects, features, and effects of the present invention will be sufficiently apparent from the following detailed description taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a chart showing a lens arrangement of a zoom lens according to the first embodiment of the present invention;

FIG. 2 is a chart showing a lens arrangement of a zoom lens according to the second embodiment of the present invention;

FIG. 3 is a chart showing a lens arrangement of a zoom lens according to the third embodiment of the present invention;

FIG. 4 is a chart showing a lens arrangement of a zoom lens according to the fourth embodiment of the present invention;

FIG. 5 is a chart showing a lens arrangement of a zoom lens according to the fifth embodiment of the present invention;

FIG. 6 is a chart showing a lens arrangement of a zoom lens according to the sixth embodiment of the present invention;

FIG. 7 is a chart showing a lens arrangement of a zoom lens according to the seventh embodiment of the present invention;

FIG. 8 is a chart showing a lens arrangement of a zoom lens according to the eighth embodiment of the present invention;

FIG. 9 is a chart showing a lens arrangement of a zoom lens according to the ninth embodiment of the present invention;

FIG. 10 is a chart showing a lens arrangement of a zoom lens according to the tenth embodiment of the present invention;

FIG. 11 is a chart showing a lens arrangement of a zoom lens according to the 11th embodiment of the present invention; and

FIG. 12 is a chart showing a lens arrangement of a zoom lens according to the 12th embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The preferred embodiments of the present invention will be described in detail hereinafter with reference to the accompanying drawings.

A zoom lens according to each embodiment includes, in turn from the object side, a first lens group G₁ having a positive refracting power, and a second lens group G₂ having a negative refracting power. When a zooming operation from the wide-angle end to the telephoto end is performed, the first and second lens groups G₁ and G₂ are moved to decrease the space therebetween.

The first lens group G₁ has, in order from the object side, a positive meniscus lens component L₁ with the convex surface facing the object side, a meniscus-shape cemented negative lens component L₂ constituted by a double-concave negative lens component L_(2n) and a double-convex positive lens component L_(2p), and a double-convex lens component L₃. The second lens group G₂ has a positive meniscus lens component L₄ with the convex surface facing the image side, and a negative meniscus lens component L₅ with the convex surface facing the image side.

In each embodiment, the second lens group G₂ has an aspherical lens surface.

The specifications of the embodiments of the present invention will be presented below. In a table summarizing the specifications of each embodiment, the radius of curvature (the paraxial radius of curvature in the case of an aspherical surface) of the i-th (i=1, 2, . . . ) lens surface from the object side is represented by r_(i), the lens surface interval between the i-th surface and the (i+1)-th surface is represented by d_(i), the Abbe's number of a medium between the i-th surface and the (i+1)-th surface is represented by ν_(di), and the refractive index of the medium between the i-th surface and the (i+1)-th surface with respect to a d-line (λ=587.6 nm) is represented by n_(i). In addition, f is the focal length of the entire system, F_(N0) is the f-number, and 2ω is the field angle.

The aspherical surface shape arranged in the second lens group G₂ of each embodiment is expressed by the following aspherical surface formula: ##EQU1## where X(y) is the distance along the optical axis from the tangent plane tangent to the vertex of the aspherical surface to the position of a height y on the aspherical surface, r is the paraxial radius of curvature, C_(n) (n=2 to 10) is the aspherical surface coefficient, and k is the conic constant of the aspherical surface.

First Embodiment

FIG. 1 is a chart showing the lens arrangement of the first embodiment at the wide-angle end. An aperture stop S is arranged immediately after the first lens group G₁. When the first and second lens groups G₁ and G₂ are respectively moved along moving paths D₁ and D₂ to decrease a gap therebetween, a zooming operation to the telephoto end is attained while maintaining a constant image surface. The components of the moving paths D₁ and D₂ in the optical axis direction (Z direction) indicate the positions of the corresponding lens groups on the optical axis, and the components in a direction (f direction) perpendicular to the optical axis direction indicate the focal lengths.

A focusing operation to a short-distance object may be attained by moving the first lens group G₁ toward the object side, by moving the second lens group G₂ toward the image-surface side, or by moving the entire zoom lens toward the object side. The same applies to the following embodiments.

Table 1 summarizes the specifications of the first embodiment. In this embodiment, since a zooming operation is performed by changing a surface interval d₇, the values of the focal length f of the entire system and a back focus B.f. (=surface interval d₁₁) obtained when the surface interval d₇ is varied are added after the lens data of Table 1. In the first embodiment, the eighth surface is the aspherical surface, and Table 2 summarizes the values of the aspherical coefficients and the conic constant.

                  TABLE 1                                                          ______________________________________                                         Specifications of the First Embodiment                                                    f = 39.0 to 63.1                                                               F.sub.NO = 4.00 to 6.47                                                        2ω = 56.7° to 37.7°                             i        r.sub.i  d.sub.i      ν.sub.di                                                                         n.sub.i                                    ______________________________________                                         1        14.033   1.80         53.9 1.71300                                    2        29.125   1.70                                                         3        -14.454  1.30         45.0 1.74400                                    4        14.454   4.00         69.9 1.51860                                    5        -12.206  1.00                                                         6        33.099   2.00         64.1 1.51680                                    7        -33.099  variable                                                     8        -30.944  2.10         35.0 1.74950                                    9        -16.691  3.00                                                         10       -9.504   1.20         53.9 1.71300                                    11       -60.319  (B.f.)                                                       f       39.0003       50.0008 63.1015                                          d.sub.7  9.6422        5.9755  3.2766                                          B.f.    14.6038       26.0441 39.6687                                          ______________________________________                                    

                  TABLE 2                                                          ______________________________________                                         Aspherical Surface Shape of Eighth                                             Surface of the First Embodiment                                                ______________________________________                                                   k = 0.0000                                                                     C.sub.2 = 0.0000                                                               C.sub.4 = 0.4357 × 10.sup.-4                                             C.sub.6 = 0.7315 × 10.sup.-6                                             C.sub.8 = -0.7453 × 10.sup.-8                                            C.sub.10 = 0.1202 × 10.sup.-9                                  ______________________________________                                    

Second Embodiment

FIG. 2 is a chart showing the lens arrangement of the second embodiment. In the second embodiment, the eighth surface is also the aspherical surface, and Tables 3 and 4 below summarize the specifications of the second embodiment, and the aspherical surface coefficients and the like of the eighth surface.

                  TABLE 3                                                          ______________________________________                                         Specifications of the Second Embodiment                                                   f = 36.0 to 58.2                                                               F.sub.NO = 4.01 to 6.49                                                        2ω = 60.6° to 40.8°                             i        r.sub.i  d.sub.i      v.sub.di                                                                            n.sub.i                                    ______________________________________                                         1        13.041   1.80         50.2 1.72000                                    2        22.562   2.20                                                         3        -13.744  1.30         45.0 1.74400                                    4        13.553   4.00         69.9 1.51860                                    5        -11.234  1.00                                                         6        20.988   2.00         64.1 1.51680                                    7        -56.402  variable                                                     8        -25.724  2.10         35.0 1.74950                                    9        -15.133  3.00                                                         10       -9.539   1.20         53.9 1.71300                                    11       -60.568  (B.f.)                                                       f       36.0006       45.0008 58.2016                                          d.sub.7  9.4060        5.9394  2.7944                                          B.f.    12.9007       22.6508 36.9513                                          ______________________________________                                    

                  TABLE 4                                                          ______________________________________                                         Aspherical Surface Shape of Eighth Surface                                     of the Second Embodiment                                                       ______________________________________                                                   k = 0.0000                                                                     C.sub.2 = 0.0000                                                               C.sub.4 = 0.3012 × 10.sup.-4                                             C.sub.6 = 0.4606 × 10.sup.-6                                             C.sub.8 = -0.3136 × 10.sup.-8                                            C.sub.10 = 0.7047 × 10.sup.-10                                 ______________________________________                                    

Third Embodiment

FIG. 3 is a chart showing the lens arrangement of the third embodiment. In the third embodiment, the ninth surface is the aspherical surface, and Tables 5 and 6 below summarize the specifications of the third embodiment, and the aspherical surface coefficients and the like of the ninth surface.

                  TABLE 5                                                          ______________________________________                                         Specifications of the Third Embodiment                                                    f = 39.0 to 63.1                                                               F.sub.NO = 4.00 to 6.47                                                        2ω = 56.5° to 37.6°                             i        r.sub.i  d.sub.i      v.sub.di                                                                            n.sub.i                                    ______________________________________                                         1        14.035   1.80         53.9 1.71300                                    2        31.724   1.70                                                         3        -15.075  1.20         45.0 1.74400                                    4        13.523   4.30         69.9 1.51860                                    5        -13.523  0.10                                                         6        60.040   2.00         60.7 1.56384                                    7        -24.231  variable                                                     8        -21.267  2.10         31.6 1.75692                                    9        -14.846  3.60                                                         10       -9.603   1.20         53.9 1.71300                                    11       -43.484  (B.f.)                                                       f       39.0005       50.0012 63.1024                                          d.sub.7  9.9458        6.2791  3.5802                                          B.f.    14.0931       25.5336 39.1585                                          ______________________________________                                    

                  TABLE 6                                                          ______________________________________                                         Aspherical Surface Shape of Ninth Surface                                      of the Third Embodiment                                                        ______________________________________                                                   k = 0.1077 × 10.sup.+1                                                   C.sub.2 = 0.0000                                                               C.sub.4 = -0.3206 × 10.sup.-4                                            C.sub.6 = -0.3118 × 10.sup.-6                                            C.sub.8 = -0.4991 × 10.sup.-8                                            C.sub.10 = -0.3329 × 10.sup.-11                                ______________________________________                                    

Fourth Embodiment

FIG. 4 is a chart showing the lens arrangement of the fourth embodiment. In the fourth embodiment, the 11th surface is the aspherical surface, and Tables 7 and 8 below summarize the specifications of the fourth embodiment, and the aspherical surface coefficients and the like of the 11th surface.

                  TABLE 7                                                          ______________________________________                                         Specifications of the Fourth Embodiment                                                   f = 39.0 to 63.1                                                               F.sub.NO = 4.00 to 6.47                                                        2ω = 56.8° to 37.7°                             i        r.sub.i  d.sub.i      v.sub.di                                                                            n.sub.i                                    ______________________________________                                         1        14.173   1.80         55.6 1.69680                                    2        30.934   1.70                                                         3        -14.476  1.20         45.0 1.74400                                    4        14.476   4.30         69.9 1.51860                                    5        -12.645  0.10                                                         6        45.737   2.30         60.7 1.56384                                    7        -28.834  variable                                                     8        -16.791  2.10         31.6 1.75692                                    9        -12.676  3.60                                                         10       -10.451  1.20         53.9 1.71300                                    11       -65.212  (B.f.)                                                       f       39.0006       50.0015 63.1030                                          d.sub.7 10.3636        6.6969  3.9980                                          B.f.    13.9256       25.3662 38.9913                                          ______________________________________                                    

                  TABLE 8                                                          ______________________________________                                         Aspherical Surface Shape of 11th Surface                                       of the Fourth Embodiment                                                       ______________________________________                                                   k = -0.9151 × 10.sup.+1                                                  C.sub.2 = 0.0000                                                               C.sub.4 = 0.3130 × 10.sup.-4                                             C.sub.6 = 0.3607 × 10.sup.-6                                             C.sub.8 = -0.5020 × 10.sup.-8                                            C.sub.10 = 0.1939 × 10.sup.-10                                 ______________________________________                                    

Fifth Embodiment

FIG. 5 is a chart showing the lens arrangement of the fifth embodiment. In the fifth embodiment, the eighth surface is the aspherical surface, and Tables 9 and 10 below summarize the specifications of the fifth embodiment, and the aspherical surface coefficients and the like of the eighth surface.

                  TABLE 9                                                          ______________________________________                                         Specifications of the Fifth Embodiment                                                    f = 39.0 to 63.1                                                               F.sub.NO = 4.11 to 6.66                                                        2ω = 56.7° to 37.7°                             i        r.sub.i  d.sub.i      ν.sub.di                                                                         n.sub.i                                    ______________________________________                                         1        14.320   1.80         55.6 1.69680                                    2        31.046   1.70                                                         3        -14.477  1.20         45.0 1.74400                                    4        14.477   4.30         69.9 1.51860                                    5        -12.897  0.10                                                         6        46.312   2.30         60.7 1.56384                                    7        -27.107  variable                                                     8        -22.353  2.10         31.6 1.75692                                    9        -15.730  3.60                                                         10       -9.612   1.20         53.9 1.71300                                    11       -40.057  (B.f.)                                                       f       39.0006       50.0014 63.1028                                          d.sub.7 10.3364        6.6697  3.9708                                          B.f.    13.9930       25.4338 39.0591                                          ______________________________________                                    

                  TABLE 10                                                         ______________________________________                                         Aspherical Surface Shape of Eighth Surface                                     of the Fifth Embodiment                                                        ______________________________________                                                   k = 0.0000                                                                     C.sub.2 = 0.0000                                                               C.sub.4 = 0.3155 × 10.sup.-4                                             C.sub.6 = 0.5395 × 10.sup.-6                                             C.sub.8 = -0.6964 × 10.sup.-9                                            C.sub.10 = 0.4240 × 10.sup.-10                                 ______________________________________                                    

Sixth Embodiment

FIG. 6 is a chart showing the lens arrangement of the sixth embodiment. In the sixth embodiment, the eighth surface is also the aspherical surface, and Tables 11 and 12 below summarize the specifications of the sixth embodiment, and the aspherical surface coefficients and the like of the eighth surface.

                  TABLE 11                                                         ______________________________________                                         Specifications of the Sixth Embodiment                                                    f = 39.0 to 63.1                                                               F.sub.NO = 4.01 to 6.48                                                        2ω = 56.4° to 37.4°                             i        r.sub.i  d.sub.i      ν.sub.di                                                                         n.sub.i                                    ______________________________________                                         1        14.111   1.80         53.9 1.71300                                    2        33.549   1.50                                                         3        -14.031  1.30         45.0 1.74400                                    4        14.031   4.00         69.9 1.51860                                    5        -11.781  0.20                                                         6        59.921   2.00         59.0 1.51823                                    7        -27.980  variable                                                     8        -31.172  2.10         27.8 1.74077                                    9        -19.989  4.00                                                         10       -9.664   1.20         50.2 1.72000                                    11       -40.460  (B.f.)                                                       f       39.0001       50.0003 63.1006                                          d.sub.7 11.2726        7.6059  4.9070                                          B.f.    12.2073       22.7844 35.3808                                          ______________________________________                                    

                  TABLE 12                                                         ______________________________________                                         Aspherical Surface Shape of Eighth Surface                                     of the Sixth Embodiment                                                        ______________________________________                                                   k = 0.0000                                                                     C.sub.2 = 0.0000                                                               C.sub.4 = 0.3925 × 10.sup.-4                                             C.sub.6 = 0.1301 × 10.sup.-5                                             C.sub.8 = -0.1772 × 10.sup.-7                                            C.sub.10 = 0.1695 × 10.sup.-9                                  ______________________________________                                    

Seventh Embodiment

FIG. 7 is a chart showing the lens arrangement of the seventh embodiment. In the seventh embodiment, the tenth surface is the aspherical surface, and Tables 13 and 14 below summarize the specifications of the seventh embodiment, and the aspherical surface coefficients and the like of the tenth surface.

                  TABLE 13                                                         ______________________________________                                         Specifications of the Seventh Embodiment                                                  f = 39.0 to 63.1                                                               F.sub.NO = 4.00 to 6.46                                                        2ω = 56.6° to 37.7°                             i        r.sub.i  d.sub.i      ν.sub.di                                                                         n.sub.i                                    ______________________________________                                         1        13.693   1.80         55.6 1.69680                                    2        29.737   1.70                                                         3        -15.115  1.30         45.0 1.74400                                    4        13.878   4.40         69.9 1.51860                                    5        -12.550  0.20                                                         6        38.818   2.00         60.7 1.56384                                    7        -38.818  variable                                                     8        -21.394  2.10         35.0 1.74950                                    9        -13.074  3.00                                                         10       -9.525   1.20         53.9 1.71300                                    11       -66.661  (B.f.)                                                       f       39.0003       50.0004 63.1005                                          d.sub.7 10.1954        6.3268  3.4793                                          B.f.    14.4196       26.1126 40.0378                                          ______________________________________                                    

                  TABLE 14                                                         ______________________________________                                         Aspherical Surface Shape of Tenth Surface                                      of the Seventh Embodiment                                                      ______________________________________                                                   k = 0.0000                                                                     C.sub.2 = 0.0000                                                               C.sub.4 = -0.1024 × 10.sup.-3                                            C.sub.6 = -0.4683 × 10.sup.-6                                            C.sub.8 = 0.5245 × 10.sup.-8                                             C.sub.10 = -0.6514 × 10.sup.-10                                ______________________________________                                    

Eighth Embodiment

FIG. 8 is a chart showing the lens arrangement of the eighth embodiment. In the eighth embodiment, the eighth surface is the aspherical surface, and Tables 15 and 16 below summarize the specifications of the eighth embodiment, and the aspherical surface coefficients and the like of the eighth surface.

                  TABLE 15                                                         ______________________________________                                         Specifications of the Eighth Embodiment                                                   f = 39.0 to 63.1                                                               F.sub.NO = 4.10 to 6.63                                                        2ω = 56.7° to 37.7°                             i        r.sub.i  d.sub.i      ν.sub.di                                                                         n.sub.i                                    ______________________________________                                         1        13.823   2.00         57.0 1.62280                                    2        34.400   1.45                                                         3        -14.361  1.20         45.0 1.74400                                    4        14.361   4.30         69.9 1.51860                                    5        -12.556  0.10                                                         6        46.841   2.30         56.1 1.56883                                    7        -28.975  variable                                                     8        -22.324  2.10         37.0 1.81474                                    9        -16.019  3.60                                                         10       -9.505   1.20         55.6 1.69680                                    11       -41.707  (B.f.)                                                       f       39.0002       50.0021 63.0985                                          d.sub.7 10.3950        6.7280  4.0300                                          B.f.    13.9859       25.4275 39.0473                                          ______________________________________                                    

                  TABLE 16                                                         ______________________________________                                         Aspherical Surface Shape of Eighth Surface                                     of the Eighth Embodiment                                                       ______________________________________                                                   k = 0.0000                                                                     C.sub.2 = 0.0000                                                               C.sub.4 = 0.3011 × 10.sup.-4                                             C.sub.6 = 0.5877 × 10.sup.-6                                             C.sub.8 = -0.2123 × 10.sup.-8                                            C.sub.10 = 0.5879 × 10.sup.-10                                 ______________________________________                                    

Ninth Embodiment

FIG. 9 is a chart showing the lens arrangement of the ninth embodiment. In the ninth embodiment, the eighth surface is also the aspherical surface, and Tables 17 and 18 below summarize the specifications of the ninth embodiment, and the aspherical surface coefficients and the like of the eighth surface.

                  TABLE 17                                                         ______________________________________                                         Specifications of the Ninth Embodiment                                                    f = 39.0 to 63.1                                                               F.sub.NO = 4.11 to 6.64                                                        2ω = 56.7° to 37.7°                             i        r.sub.i  d.sub.i      ν.sub.di                                                                         n.sub.i                                    ______________________________________                                         1        12.702   2.00         64.1 1.51680                                    2        38.481   1.45                                                         3        -14.154  1.20         45.0 1.74400                                    4        14.154   4.30         64.1 1.51680                                    5        -11.897  0.10                                                         6        40.460   2.30         58.5 1.61272                                    7        -40.460  variable                                                     8        -22.343  2.10         40.5 1.73077                                    9        -15.717  3.60                                                         10       -9.112   1.20         60.0 1.64000                                    11       -43.688  (B.f.)                                                       f       39.0008       49.9992 63.1000                                          d.sub.7 10.3220        6.6560  3.9570                                          B.f.    13.9749       25.4128 39.0370                                          ______________________________________                                    

                  TABLE 18                                                         ______________________________________                                         Aspherical Surface Shape of Eighth Surface                                     of the Ninth Embodiment                                                        ______________________________________                                                   k = 0.0000                                                                     C.sub.2 = 0.0000                                                               C.sub.4 = 0.3967 × 10.sup.-4                                             C.sub.6 = 0.7701 × 10.sup.-6                                             C.sub.8 = -0.4227 × 10.sup.-8                                            C.sub.10 = 0.1057 × 10.sup.-9                                  ______________________________________                                    

Tenth Embodiment

FIG. 10 is a chart showing the lens arrangement of the tenth embodiment. In the tenth embodiment, the eighth surface is also the aspherical surface, and Tables 19 and 20 below summarize the specifications of the tenth embodiment, and the aspherical surface coefficients and the like of the eighth surface.

                  TABLE 19                                                         ______________________________________                                         Specifications of the Tenth Embodiment                                                    f = 39.0 to 63.1                                                               F.sub.NO = 4.11 to 6.64                                                        2ω = 56.6° to 37.7°                             i        r.sub.i  d.sub.i      ν.sub.di                                                                         n.sub.i                                    ______________________________________                                         1        13.495   2.00         58.5 1.61272                                    2        44.225   1.20                                                         3        -15.587  1.20         39.6 1.80454                                    4        15.587   4.30         59.0 1.51823                                    5        -13.242  0.10                                                         6        206.972  2.30         46.5 1.80411                                    7        -28.299  variable                                                     8        -22.785  2.10         37.0 1.81474                                    9        -16.134  3.60                                                         10       -9.851   1.20         49.4 1.77279                                    11       -36.468  (B.f.)                                                       f       39.0010       49.9992 63.1000                                          d.sub.7 10.5689        6.9030  4.2040                                          B.f.    14.0020       25.4397 39.0640                                          ______________________________________                                    

                  TABLE 20                                                         ______________________________________                                         Aspherical Surface Shape of Eighth Surface                                     of the Tenth Embodiment                                                        ______________________________________                                                   k = 0.0000                                                                     C.sub.2 = 0.0000                                                               C.sub.4 = 0.2748 × 10.sup.-4                                             C.sub.6 = 0.5416 × 10.sup.-6                                             C.sub.8 = -0.1523 × 10.sup.-8                                            C.sub.10 = 0.4006 × 10.sup.-10                                 ______________________________________                                    

11th Embodiment

FIG. 11 is a chart showing the lens arrangement of the 11th embodiment. In the 11th embodiment, the eighth surface is also the aspherical surface, and Tables 21 and 22 below summarize the specifications of the 11th embodiment, and the aspherical surface coefficients and the like of the eighth surface.

                  TABLE 21                                                         ______________________________________                                         Specifications of the 11th Embodiment                                                     f = 39.0 to 68.0                                                               F.sub.NO = 4.09 to 7.13                                                        2ω = 56.8° to 35.0°                             i        r.sub.i  d.sub.i      ν.sub.di                                                                         n.sub.i                                    ______________________________________                                         1        14.141   2.00         45.9 1.54814                                    2        49.596   1.45                                                         3        -13.789  1.20         40.9 1.79631                                    4        16.887   4.30         64.1 1.51680                                    5        -11.932  0.10                                                         6        44.929   2.30         59.0 1.51823                                    7        -24.795  variable                                                     8        -29.709  2.10         37.0 1.81474                                    9        -18.512  3.60                                                         10       -9.681   1.20         55.6 1.69680                                    11       -53.162  (B.f.)                                                       f       39.0002       50.0005 68.0003                                          d.sub.7 12.2358        8.4224  4.8437                                          B.f.    12.9091       23.9095 41.9091                                          ______________________________________                                    

                  TABLE 22                                                         ______________________________________                                         Aspherical Surface Shape of Eighth Surface                                     of the 11th Embodiment                                                         ______________________________________                                                   k =  0.0000                                                                    C.sub.2 = 0.0000                                                               C.sub.4 = 0.3456 × 10.sup.-4                                             C.sub.6 = 0.9885 × 10.sup.-6                                             C.sub.8 = -0.1326 × 10.sup.-7                                            C.sub.10 = 0.1499 × 10.sup.-9                                  ______________________________________                                    

12th Embodiment

FIG. 12 is a chart showing the lens arrangement of the 12th embodiment. In the 12th embodiment, the eighth surface is also the aspherical surface, and Tables 23 and 24 below summarize the specifications of the 12th embodiment, and the aspherical surface coefficients and the like of the eighth surface.

                  TABLE 23                                                         ______________________________________                                         Specifications of the 12th Embodiment                                                     f = 36.0 to 68.0                                                               F.sub.NO = 4.10 to 7.74                                                        2ω = 60.8° to 35.4°                             i        r.sub.i  d.sub.i      ν.sub.di                                                                         n.sub.i                                    ______________________________________                                         1        14.424   2.00         38.0 1.60342                                    2        29.870   2.00                                                         3        -13.961  1.20         40.9 1.79631                                    4        17.019   4.30         64.1 1.51680                                    5        -11.539  1.00                                                         6        24.938   2.30         69.9 1.51860                                    7        -37.713  variable                                                     8        -28.050  2.60         37.0 1.81474                                    9        -17.613  3.60                                                         10       -9.898   1.20         55.6 1.69680                                    11       -57.061  (B.f.)                                                       f       36.0001       50.0002 68.0006                                          d.sub.7 13.2090        7.7490  4.0325                                          B.f.    10.1790       24.7176 43.4102                                          ______________________________________                                    

                  TABLE 24                                                         ______________________________________                                         Aspherical Surface Shape of Eighth Surface                                     of the 12th Embodiment                                                         ______________________________________                                                   k = 0.0000                                                                     C.sub.2 = 0.0000                                                               C.sub.4 = 0.2711 × 10.sup.-4                                             C.sub.6 = 0.7873 × 10.sup.-6                                             C.sub.8 = -0.9386 × 10.sup.-8                                            C.sub.10 = 0.1025 × 10.sup.-9                                  ______________________________________                                    

The zoom lens according to the present invention is preferably arranged to satisfy the conditions (1) to (4). Thus, Table 25 below summarizes data of the respective embodiments for the conditions (1) to (4).

                  TABLE 25                                                         ______________________________________                                         Condition Correspondence Table (1)                                             Embodiments                                                                              dL.sub.2 /f.sub.W                                                                      (nL.sub.2n -nL.sub.2p) · f.sub.W /r.sub.4                                           fL.sub.2 /f.sub.1                                                                    fL.sub.3 /f.sub.1                        ______________________________________                                         1st       0.136   0.608         -2.504                                                                               1.294                                    2nd       0.147   0.599         -2.830                                                                               1.244                                    3rd       0.141   0.650         -2.030                                                                               1.235                                    4th       0.141   0.607         -2.324                                                                               1.269                                    5th       0.141   0.607         -2.199                                                                               1.227                                    6th       0.136   0.627         -2.422                                                                               1.427                                    7th       0.146   0.633         -2.571                                                                               1.368                                    8th       0.141   0.612         -2.309                                                                               1.273                                    9th       0.141   0.626         -2.553                                                                               1.335                                    10th      0.141   0.716         -1.793                                                                               1.244                                    11th      0.141   0.646         -1.853                                                                               1.199                                    12th      0.153   0.591         -2.115                                                                               1.127                                    ______________________________________                                    

Furthermore, the zoom lens according to the present invention is preferably arranged to satisfy the conditions (5) to (7) under the above-mentioned conditions (1) to (4). Table 26 below summarizes data for the respective embodiments corresponding to the conditions (5) to (7).

                  TABLE 26                                                         ______________________________________                                         Condition Correspondence Table (2)                                                                    fL.sub.1 ·                                     Embodiments                                                                               Σd.sub.W /f.sub.W                                                                    L.sub.2 /f.sub.1                                                                        νL.sub.2p -νL.sub.2n                     ______________________________________                                         1st        0.711       4.176    24.9                                           2nd        0.778       4.940    24.9                                           3rd        0.717       4.890    24.9                                           4th        0.735       4.672    24.9                                           5th        0.734       5.440    24.9                                           6th        0.753       3.235    24.9                                           7th        0.715       3.590    24.9                                           8th        0.734       4.708    24.9                                           9th        0.733       4.091    19.1                                           10th       0.733       4.956    19.4                                           11th       0.782       7.142    23.2                                           12th       0.928       13.113   23.2                                           ______________________________________                                    

The present invention is not limited to the above embodiments, and various other arrangements may be adopted without departing from the scope of the invention. 

What is claimed is:
 1. A zoom lens, which includes a first lens group G₁ having a positive refracting power and a second lens group G₂ having a negative refracting power, and performs a zooming operation from a wide-angle end to a telephoto end by decreasing a space between said first and second lens groups G₁ and G₂, whereinsaid first lens group G₁ has, in order from an object side, a positive meniscus lens component L₁ with a convex surface facing the object side, a cemented negative lens component L₂ constituted by a double-concave negative lens component L_(2n) and a double-convex positive lens component L_(2p), and having a meniscus shape as a whole, and a double-convex positive lens component L₃, said second lens group G₂ has, in order from the object side, a positive meniscus lens component L₄ with a convex surface facing an image side, and a negative meniscus lens component L₅ with a convex surface facing the image side, and said zoom lens is arranged to satisfy the following conditions:

    0.09<dL.sub.2 /f.sub.W <0.18

    0.45<(nL.sub.2n -nL.sub.2p)·f.sub.W /r.sub.4 <0.9

    -4<fL.sub.2 /f.sub.1 <-1.8

    1.1<fL.sub.3 /f.sub.1 <1.6

wheref_(W) : the focal length of the entire system at the wide-angle end dL₂ : the axial lens thickness of said cemented negative lens component L₂ in said first lens group G₁ nL_(2n) : the refractive index of said double-concave negative lens component L_(2n) forming said cemented negative lens component L₂ in said first lens group G₁ nL_(2p) : the refractive index of said double-convex positive lens component L_(2p) forming said cemented negative lens component L₂ in said first lens group G₁ r₄ : the radius of curvature of the junction surface in said cemented negative lens component L₂ in said first lens group G₁ fL₂ : the focal length of said cemented negative lens component L₂ in said first lens group G₁ fL₃ : the focal length of said double-convex positive lens component L₃ in said first lens group G₁ f₁ : the focal length of said first lens group G₁.
 2. A zoom lens according to claim 1, wherein said zoom lens is arranged to satisfy the following conditions:

    0.5<Σd.sub.W /f.sub.W <0.85

    2<fL.sub.1 ·L.sub.2 /f.sub.1 <9

where Σd_(W) : the axial lens thickness from the most object-side lens surface to the most image-side lens surface of said zoom lens at the wide-angle end fL₁ ·L₂ : the composite focal length of said positive meniscus lens component L₁ and said cemented negative lens component L₂ in said first lens group G₁.
 3. A zoom lens according to claim 2, wherein at least one lens surface in said second lens group G₂ is formed to have an aspherical surface shape.
 4. A zoom lens according to claim 3, wherein said zoom lens is arranged to satisfy the following condition:

    17<νL.sub.2p -νL.sub.2n <30

where νL_(2p) : the Abbe's number of said double-convex positive lens component L_(2p) forming said cemented negative lens component L₂ in said first lens group G₁ νL_(2n) : the Abbe's number of said double-concave negative lens component L_(2n) forming said cemented negative lens component L₂ in said first lens group G₁.
 5. A zoom lens according to claim 3, wherein the aspherical surface shape in said second lens group G₂ is formed so that a positive refracting power is gradually increased from the optical axis toward a peripheral portion on the aspherical surface.
 6. A zoom lens according to claim 5, wherein said zoom lens is arranged to satisfy the following condition:

    17<νL.sub.2p -νL.sub.2n <30

where νL_(2p) : the Abbe's number of said double-convex positive lens component L_(2p) forming said cemented negative lens component L₂ in said first lens group G₁ νL_(2n) : the Abbe's number of said double-concave negative lens component L_(2n) forming said cemented negative lens component L₂ in said first lens group G₁.
 7. A zoom lens according to claim 3, wherein the aspherical surface shape in said second lens group G₂ is formed so that a negative refracting power is gradually decreased from the optical axis toward a peripheral portion on the aspherical surface.
 8. A zoom lens according to claim 7, wherein said zoom lens is arranged to satisfy the following condition:

    17<νL.sub.2p -νL.sub.2n <30

where νL_(2p) : the Abbe's number of said double-convex positive lens component L_(2p) forming said cemented negative lens component L₂ in said first lens group G₁ νL_(2n) : the Abbe's number of said double-concave negative lens component L_(2n) forming said cemtend negative lens component L₂ in said first lens group G₁.
 9. A zoom lens according to claim 1, wherein at least one lens surface in said second lens group G₂ is formed to have an aspherical surface shape.
 10. A zoom lens according to claim 9, wherein said zoom lens is arranged to satisfy the following condition:

    1<ν L.sub.2p -νL.sub.2n <30

where νL_(2p) : the Abbe's number of said double-convex positive lens component L_(2p) forming said cemented negative lens component L₂ in said first lens group G₁ νthe Abbe's number of said double-concave negative lens component L_(2n) forming said cemented negative lens component L₂ in said first lens group G₁. 